Trench warfare was a military strategy that  involved soldiers digging and occupying long, defensive trenches to protect themselves from enemy fire. This tactic led to fatigue, static battles, with both sides facing immense casualties while making little progress (stalemate). The trenches were often muddy, unsanitary, and cramped, contributing to high rates of disease and psychological trauma. 

Source of Visual: BBC

The main reason tanks were introduced during WWI was to overcome trench defenses and break the stalemate. During WWI, tanks were used on the Western Front primarily to lead infantry advances across no man's land and into enemy territory. They helped break the stalemate of trench warfare.

Source of Visual: (National Library of Scotland) 

Poison gas was used during WWI to attack enemy troops by causing suffocation, blindness, or debilitating injuries, often leading to panic and disorientation. The U.S. developed protective masks during WWI to shield soldiers from chemical weapons used in the war and protect them from the effects of poison gas.

Source of Visual: https://www.historynet.com/weapons-of-world-war-i/

The use of machine guns led to massive casualties, resulting in a stalemate along the Western Front.

Source of Visual: https://www.historynet.com/weapons-of-world-war-i/

The Espionage Act of 1917 made it a crime to interfere with military recruitment or to promote insubordination in the military, significantly restricting freedom of speech during World War I. 

The Sedition Act of 1918 made it a crime to criticize the government or the war effort, further restricting freedom of speech during World War I. 

The League of Nations was an organization created after World War I to help countries work together and avoid future wars. It was meant to encourage peace and cooperation between countries. However, the U.S. Senate did not want America to join because they wanted to keep the country independent in making its own decisions. They believed that cooperation among world leaders was important, but they didn't want to give up too much control over U.S. actions.

Isolationism in the U.S. after World War I refers to the country's desire to stay out of foreign conflicts and avoid involvement in international politics. After the war, many Americans wanted to focus on domestic issues rather than getting involved in the problems of other countries. This was partly because the U.S. had suffered heavy losses during the war and wanted to avoid future entanglements. As a result, the U.S. did not join the League of Nations and tried to keep its distance from European and global political alliances.